Explore the highlights of the Big Bang model, which says that the universe evolved from an initial hot, dense state billions of years ago. Find that the Big Bang wasn’t a moment when the cosmos had zero size, it didn’t take place at a special point in space, and it wasn’t necessarily the beginning of the universe. Rather, it was the energetic start of the expansion phase that is still underway.
Beginning a hundred-billionth of a second after the Big Bang, trace events as the universe quickly cooled from a quadrillion degrees. Learn about the strong, weak, and electromagnetic forces, and the fundamental particles—all of which precipitated from the seething cauldron of energy, even as matter and antimatter were mutually annihilating. Within 3 minutes, hydrogen and helium nuclei had begun to form.
Continue the story of the early universe by exploring such highlights as the formation of the first atoms at 370,000 years, when space transitioned from opaque to transparent; the accretion of hydrogen and helium gas into protogalaxies after millions of years due to the gravitational influence of dark matter; and the collapse of the gas into ever denser balls eventually leading to the first stars.
Is it possible to calculate the size of the universe at the instant of the Big Bang? Assemble the clues that scientists use to address this question. In the process, discover a number of remarkable properties of the universe, including that it must be bigger that what we can see, extending beyond the boundary that limits our knowledge due to the finite speed of light and the age of the universe.
Evaluate three mysteries connected to the Big Bang model that baffled theorists beginning in the late 1960s. Why was the early universe so uniform? Why does the universe obey the laws of geometry we teach in high school? And how did the universe come to be made of the kinds of particles we see and not others? A single solution to all three questions seemed too much to hope for, yet one turned up.
Dig into the bizarre theory of inflation developed by physicist Alan Guth, which holds that for a fraction of a second just after the Big Bang the universe expanded at a mind-boggling rate, making the cosmos effectively infinite. Analyze how this idea solves the three puzzles introduced in Lecture 5. Learn about associated concepts, such as the scalar field and its decay, known as “reheating.”
Can inflation possibly be true? See how a concept called a scalar field may be the inconceivably high-energy medium that spontaneously triggered inflation, leading to the observable universe—and more—in a billionth of a billionth of a billionth of a billionth of a second. Probe a rival theory that the Big Bang was caused by the collision of two universes in four-dimensional space.
At one time, Earth was considered the center of the cosmos. Might the idea that the Big Bang was the beginning of everything be just as parochial? Take a mindboggling trip through the theory of eternal inflation—that our observable universe is a nearly infinitesimal speck inside a much larger, older, and eternally growing multiverse, in which inflation continually sprouts new universes like ours.
Many physicists believe that our universe really isn’t three dimensional, but only appears so to us. Explore what it would mean if there are extra dimensions that we can’t see. Learn how to visualize this counterintuitive state, and examine what it implies for Big Bang theory and the concept of a multiverse. One set of ideas that calls for at least nine dimensions is string theory.
Constants of nature, such as the gravitational constant, appear to be fine-tuned to make life possible. Is this a coincidence of astronomical unlikelihood, an expected outcome of the nature of the universe, or does it imply that ours is one of many universes with different properties? Consider this question in light of the anthropic principle which takes the existence of observers into account.
Learn that the ultimate fate of the universe is tied to its beginning—to the as-yet-unknown conditions that preceded the Big Bang. Focus on the importance of dark energy, an enigmatic force discovered in the 1990s that is causing the universe to expand at an accelerating rate. Compare three scenarios that lead to either infinite expansion or eventual collapse in a Big Crunch.
Conclude the course by reviewing the history of the universe, highlighting the major gaps in our knowledge. Then turn to four promising areas of experimental research that may provide answers. Let your imagination soar by contemplating theoretical possibilities such as this one: Could we exploit inflation to create a baby universe in the lab? Do we, in fact, live in someone else’s baby universe?